1. Field of the Invention
This invention is generally directed to methods for controlling growth of parasitic plants and more particularly to a method for destroying mistletoe using oils without causing harm to host trees affected by the mistletoe and without adverse affect to the environment.
2. Brief Description of the Related Art
Mistletoe is a parasitic plant that grows on conifers, hardwoods, ornamental trees, fruit trees and the like. Mistletoe robs nutrients and water from the host plant as well as produces its own additional nutrients in the same manner as other plants. There are two species of mistletoe in North America. Arceuthobium sp is a dwarf mistletoe that affects conifers in the Western United States. Phoradendron flavescens is a true or leafy mistletoe which affects trees in warmer climatic regions of the United States. Both species are known to cause major economic damage and can effect trees of any age or size. When a tree becomes a host to the mistletoe, if the mistletoe is allowed to flourish, the growth of the tree can be stunted and fruit and nut production seriously affected. In some cases, the mistletoe actually destroys the host tree.
There is currently no labeled chemical for control of mistletoe. Current procedures for controlling mistletoe involve pruning affected limbs of the host tree. Such pruning is a very costly and time consuming process and therefore is not economically feasible or practical in areas of heavy infestation.
In view of the foregoing, there is a need to provide a process or method to effectively control or destroy parasitic plants such as mistletoe over large expanses of acreage in a cost effective manner without adverse affect to the host plant and to the surrounding environment.
Although it has been known to control weeds and other plants by the use of oils as herbicides to terminate plant growth, it has not been known to use oils in a method nor at a time of dormancy of a host tree in order to effectively destroy mistletoe without adverse affect on the host plant and the environment.
In U.S. Pat. No. 3,063,821 to Weil, mineral oil mixtures are used to control weeds. In U.S. Pat. No. 2,554,192 to Puente et al., oils are used as herbicides. In U.S. No. Pat. 2,160,929 to Warner et al., mineral oils are used to kill plants.
The present invention is directed to a method of destroying mistletoe which does not adversely affect host plants and trees by the application of a physical barrier to the surface of the mistletoe plant which is applied, such as by spray application, during a dormancy period of the host tree or plant. In accordance with the invention, complete surface coverage of the mistletoe plant is promoted during the dormancy period of a host as there is reduced foliage which could otherwise block the application of the physical barrier which, in the preferred embodiment, is by way of an oil which is sprayed on the surface of the mistletoe. The oil blocks the stomatal openings and thereby interrupts the intake of carbon dioxide and water to the mistletoe which causes a shutdown of the metabolic process. In accordance with the process, when the host plant is dormant, it is not furnishing any nutrients to the parasitic plant. The lack of nutrients from the host plant timed together with the interruption of the intake of carbon dioxide and water to the mistletoe facilitates the destruction of the mistletoe.
The oils used as a physical coating or barrier in accordance with the process includes those which are readily available on the market including natural unrefined oils such as vegetable oils. The oils must be applied in sufficient strength and must have sufficient viscosity to create physical barriers that will not be washed from the surface of the mistletoe during snow, heavy dew, or rainfall as the time required for destruction of the mistletoe may extend several months in duration. Thus, the surface coating either must be maintained or reapplied during this period.
It is a primary object of the present invention to provide a process which effectively destroys mistletoe with minimal harm to a host tree and its fruit or nuts and which is completely safe to the environment and not harmful to individuals using the process.